An improved-two stage detection technique for IEEE 802.22 WRAN

In wireless regional area networks (WRAN's), spectrum sensing (SS) is one of the vital functions who detects primary users (PU) licensed signal for cognitive radios. In this paper, an improved-two stage detection (improved-TSD) technique for spectrum sensing has been proposed. In improved-TSD technique, two detectors (energy detector with single adaptive threshold (ED_SAT) and energy detector with two adaptive thresholds (ED_TAT)) work simultaneously, and then based on the decision of both detectors final decision has been takes place by decision device (DD) using OR-rules. Detectors have adaptive thresholds, ED_SAT has single adaptive threshold and ED_TAT has two adaptive thresholds. Thresholds depend on noise variance (σω2), and noise variance value changes according to noise signal. Due to this, the values of thresholds also change. Therefore, the thresholds are adaptive thresholds. Graphical results confirm that proposed improved-TSD technique improves detection performance and outperforms the multiple-ED and ED with adaptive double thresholds detector-2013 (MED and ED-ADT-2013), energy detection technique for adaptive spectrum sensing-2015 (EDT-ASS-2015), ED and ED-ADT detector-2015, and conventional-ED by 1.4%, 10.4%, 0.5% and 31.3% at −10 dB signal-to-noise ratio (SNR) respectively. Further, in terms of sensing time the presented scheme yields smaller sensing time frame than EDT-ASS-2015 SS scheme, ED and ED-ADT detector-2015, and multiple-ED and ED-ADT detector-2013 i.e. 0.5 ms, 1.7 ms and 2.4 ms at −20 dB SNR. It is further found that cooperative SS (CSS) with improved-TSD beats hierarchical with quantization-2012 by 11.5% in terms of detection performance at −11 dB SNR, and meanwhile, it detects PU signal at −19.5 dB SNR level.